Premium
An Ephemeral Red Arc Appeared at 68° MLat at a Pseudo Breakup During Geomagnetically Quiet Conditions
Author(s) -
Oyama S.,
Shinbori A.,
Ogawa Y.,
Kellinsalmi M.,
Raita T.,
Aikio A.,
Vanhamäki H.,
Shiokawa K.,
Virtanen I.,
Cai L.,
Workayehu A. B.,
Pedersen M.,
Kauristie K.,
Tsuda T. T.,
Kozelov B.,
Demekhov A.,
Yahnin A.,
Tsuchiya F.,
Kumamoto A.,
Kasahara Y.,
Matsuoka A.,
Shoji M.,
Teramoto M.,
Lester M.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028468
Subject(s) - earth's magnetic field , substorm , arc (geometry) , geology , geomagnetic storm , geophysics , breakup , geodesy , atmospheric sciences , physics , magnetosphere , magnetic field , mechanics , quantum mechanics , geometry , mathematics
Various subauroral optical features have been studied by analyzing data collected during periods of geomagnetic disturbances. Most events have been typically found at geomagnetic latitudes of 45–60°. In this study, however, we present a red arc event found at geomagnetic 68° north ( L ≈ 7.1) in the Scandinavian sector during a period of geomagnetically quiet conditions within a short intermission between two high‐speed solar wind events. The red arc appeared to coincide with a pseudo breakup at geomagnetic 71–72°N and a rapid equatorward expansion of the polar cap. However, the red arc disappeared in approximately 7 min. Simultaneous measurements with the Swarm A/C satellites indicated the appearance of the red arc at the ionospheric trough minimum and a conspicuous enhancement of the electron temperature, suggesting the generation of the arc by heat flux. Since there are meaningful differences in the red arc features from already‐known subauroral optical features such as the stable auroral red (SAR) arc, we considered that the red arc is a new phenomenon. We suggest that the ephemeral red arc may represent the moment of SAR arc birth associated with substorm particle injection, which is generally masked by bright dynamic aurorae.